n-aryTreeBFS.js

const maxDepth = (root) => {
  //check if root is null
    if(!root) return 0
  //implement queue to complete traversing
    let queue = []
  //variable to increment while counting levels
    let depth = 0
   //push the root to the queue
    queue.push(root)
    
  //start traverse
    while(queue.length > 0){
        //n-ary with children, 
        //queue sometimes has multiple nodes of the same level
       //we need to iterate all nodes
        let size = queue.length
       //set current variable to store current node
        let current
        //loop through the queue
        for(let i = 0; i < size; i++){
          //set current as first node in the queue
            current = queue.shift()
          //iterate the children of the current node
            for(let child of current.children){
           //push child of the same level in the queue
              queue.push(child)
            }
        }
      //after iterate same level node and move to the next level
      //increment the depth by one
        depth++
    }
  
  //return the number of levels in the tree
    return depth
}